The oxidation of hydrocarbons is an important reaction in industrial organic chemistry. Thus, for example, the oxidation of cyclohexane is used commercially to produce cyclohexanol and cyclohexanone, which are important precursors in the production of nylon, whereas oxidation of alkylaromatic hydrocarbons is used to produce phenol, a precursor in the production of polycarbonates and epoxy resins.
N-substituted cyclic imides are useful as radical mediators in a number of radical based oxidation reactions. Specifically, the use of N-substituted phthalimides often allows for improved reaction rates, selectivities, and/or yields. Certain N-substituted phthalimides, particularly N-hydroxyphthalimide, are a good catalyst candidate for the oxidation of secondary butylbenzene (SBB) and cyclohexylbenzene (CHB) to their corresponding peroxides. SBB peroxide is an intermediate in the production of phenol and MEK, and CHB peroxide is an intermediate in the production of phenol and cyclohexanone.
Oxidation of hydrocarbons can be conducted using well-known oxidizing agents, such as KMnO4, CrO3 and HNO3. However, these oxidizing agents have the disadvantage that their use is accompanied by the production of unwanted side products that can pose disposal and pollution problems. Preferably, therefore, oxidizing agents based on peroxides or N2O are used. The cheapest oxidizing agent, however, is molecular oxygen, either in pure form, or as atmospheric oxygen, or in dilute form. Oxygen itself is usually unsuitable for oxidizing hydrocarbons, however, since the reactivity of the O2 molecule, which occurs in the energetically favorable triplet form, is not sufficient.
N-substituted cyclic imides useful in the oxidation of hydrocarbons suffer from the disadvantage that they are not currently available in large scale commercial quantities. As such, there are no large scale processes for the manufacture of N-substituted cyclic imides.
In accordance with the present invention, an optimized method of producing certain N-substituted cyclic imides is proposed in which N-substituted cyclic imides can be obtained in acceptable yields.